A related complementary metal oxide silicon (CMOS) image sensor includes a photodiode region for converting an optical signal to an electrical signal, and a transistor region for processing the converted electrical signal, in which the photodiode region and the transistor region are horizontally arranged. In a horizontal type CMOS image sensor, a photodiode and a transistor are horizontally formed adjacent to each other over a substrate. Therefore, an additional region for forming the photodiode is utilized, which may decrease the fill factor and limit the possibility of resolution.